The present disclosure relates to fluid pressure actuated grippers of the type employed in automated workpiece handling devices which clampingly grip and transfer a workpiece from one station to another. More particularly, the present disclosure relates to fluid pressure actuated grippers which can be locked in either or both of their closed or open positions and which are assembled from a plurality of modular or interchangeable components.
Fluid pressure actuated grippers are widely employed and typically take the form of a pneumatic or hydraulic differential motor whose cylinder is fixedly mounted to a transfer device. At the forward or rod end of the cylinder housing, a gripper jaw mounting structure is fixedly mounted on the cylinder to pivotally support a pair of opposed gripper jaws which are coupled to the piston rod of the motor by a linkage so arranged that upon movement of the piston in one direction the jaws are pivoted to an open position and upon movement of the piston in the opposite direction the jaws are driven to a closed workpiece gripping position.
In typical operation, the gripper jaws will be closed upon a workpiece near the edge of the workpiece and the gripper will be advanced to position the gripped workpiece in operative relationship with a work station. The gripper will then be opened to release the workpiece and the transfer device will retract the gripper from the work station while the work operation is performed. At the conclusion of the work operation, the gripper will then advance back into the work station and the jaws will again close upon the workpiece and carry it away from the work station. Opening and closing the gripper jaws thus takes place when the gripper is in its closest proximity to tooling at the work station.
There are basically two types of linkage arrangements used in fluid pressure actuated grippers to connect the gripper jaws to the piston rods and effect movement of the gripper jaws. These are pivotable link arrangements and pivotal cam arrangements. An example of a pivotal link arrangement can be found in U.S. Pat. No. 5,152,568 to Blatt which discloses pivotal links 36 and 40 that cooperate with gripper jaws 12A and 12B as shown in FIG. 3.
U.S. Pat. No. 4,518,187 to Blatt et al. discloses a pivotal cam arrangement in which jaw plates 45 and 47 are pivoted by the cooperation of cam slots 61 provided in the jaw plates and a pivot pin 37 (and rollers 39) attached to the piston rod.
In a typical production line, there are numerous work stations with one or more fluid pressure actuated gripper devices positioned between adjacent work stations. During operation, all of the gripper devices are synchronized so that they simultaneously remove a workpiece from one work station and transfer the workpiece to the next work station. In such an operation, a problem can occur if any one of the gripper devices fails to properly grip a workpiece. For example, if a workpiece slips from its initial gripped position it can become sufficiently out of alignment to prevent its transfer to a succeeding gripper device. A more serious problem can occur if a workpiece is transferred in a misaligned manner and subsequently positioned at a work station in a misaligned fashion. Such an incident can damage the work station. Another problem which can occur is completely losing grip of a workpiece and dropping the workpiece. Losing grip of a workpiece can occur when there is a leak or failure of fluid pressure supplied to the piston rod actuator.
Fluid pressure actuated grippers are generally designed for use with particular workpieces to be transferred and with specific work stations. For example, some workpieces and/or work stations may require wider or narrower gripper jaws, different types of gripper jaws, gripper jaws that open at different angles, different clearance requirements, etc. Because of the wide variety of design or performance options required of grippers, manufacturing facilities which utilize fluid actuated grippers typically have numerous sets of grippers which are designed to transport different workpieces between specific work stations. The requirement of stocking multiple sets of grippers adds to the manufacturer""s costs.
Accordingly an illustrative embodiment of the present disclosure provides a modular gripper assembly which comprises a body, a pair of opposable jaw members, a single cam pin and a linkage structure. The body includes a yoke structure defined at one end thereof by a pair of spaced apart wall members and a fluid driven actuator at an opposite end. A stepped-in portion is provided near the opposite end in which the stepped-in portion extends around the entire periphery of the body. The pair of opposable jaw members include tip ends which are aligned with one another. At least one of the pair of opposable jaw members is pivotal within a plane. Each of the pair of opposable jaw members has through-slots therein and is independently removable and replaceable by other jaw members. The single cam pin extends into the through-slots of each of the pair of opposable jaw members. The linkage structure is driven by the fluid driven actuator and is coupled to the single cam pin between the pair of opposable jaw members along a direction which is substantially perpendicular to the plane.
Additional features and advantages of the gripper assembly will become apparent to those skilled in the art upon consideration of the following detailed description of the illustrated embodiment exemplifying the best mode of carrying out the gripper assembly as presently perceived.